This invention is an apparatus for the measurement of the bending and torsion of a body, and, more generally, the deformation of an elastic or inelastic body induced by the application of a load or force, or by other causes, as long as the induced deformation is in the form of angular deflections, or is in such a form that it may be converted into an angular deflection. An electrical output is generated which is mathematically related to the magnitude of the load or force. In essence, this invention is a new type of strain gage which can be used as a low-cost, accurate load transducer or load cell. A principal application is in electronic weighing devices.
The most common type of strain gage measures the strain in a body by measuring the changes in the electrical resistance of a deformable resistor, which is adhered to the body at a location where strain exists. Strain in the body deforms the resistor, changing its resistance. The change in resistance is converted into an electrical signal via a bridge circuit with an external excitation electromotive force (e.m.f.). Since the amount of deformation associated with strain is usually small, the output signal is also small (the signal under maximum load is usually much less than 1% of the excitation e.m.f.). Painstaking efforts must also be undertaken in the fabrication of this type of strain gage in order to eliminate temperature and other effects. The cost of this type of strain gage is usually high.